Galactoglucomannan

Fig. 9. Partial structural formulas and shorthand notations for principal hemiceUuloses found in wood, where the sugar units ate noted as P-D-xylopyranose (Xylp), 4-Omethyl-a-D-glucopyranosyluronic acid (GlupU), a-L-arabinofuranose (Araf), P-D-glucopyranose (Glup), P-D-mannopyranose (Manp), and P-D-galactopyranose (Galp) for (a) arabino-4-O-methylglucuronoxylan from softwood, (b) 0-acetyl-galactoglucomannan from softwood, and...

CeU waUs of woods contain other subgroups of hemiceUuloses, in particular those composed primarily of D-mannopyranosyl or D-galactopyranosyl units. Glucomannans [11078-31-2] comprise 3—5% of the wood of angiosperms and 3—12% of the wood of gymnosperms. Galactoglucomannans [9040-29-3] are also common. 

Glucomannans (GM) and galactoglucomannans (GGM), common constituents of plant cell walls, are the major hemicellulosic components of the secondary cell walls of softwoods, whereas in the secondary cell walls of hardwoods they occur in minor amounts. They are suggested to be present together with xylan and fucogalactoxyloglucan in the primary cell walls of higher plants [192]. These polysaccharides were extensively studied in the 1960s [6,193]. 

Shimizu, K., Teratini, F., Hashi, M. and Miyazaki, K. (1972). Effect of the thermal treatment on wood hemicelluloses. VI. Studies on the thermal analysis of arabinogalactan, and O-acetyl and deacetylated-galactoglucomannans. Mokuzai Gakkaishi, 18(2), 79-84. 

Figure 3.4 Structures of the galactoglucomannan (a heteromannan) known to occur in the primary cell walls of several species of eudicotyledons and the glucuronoarabinoxylan (a heteroxylan) known to occur in the primary cell walls of sycamore (Acer pseudoplatanus). The structures of the heteromannans and heteroxylans in potato cell walls are unknown.

Cartier, N., Chambat, G., Josleau, J. -P. (1988). Cell wall and extracellular galactoglucomannans from suspension-cultured Rubus fmcticosus cells. Phytochemistry, 27, 1361-1364. 

Eda, S., Akiyama, Y, Kato, K., Ishizu, A., Nakano, J. (1985). A galactoglucomannan from cell walls of suspension-cultured tobacco Nicotiana tabacum) cells. Carbohydr. Res., 137, 173-181. 

Sims, I. M., Craik, D. J., Bacic, A. (1997). Structural characterization of galactoglucomannan secreted by suspension-cultured cells of Nicotiana plumbaginifolia. Carbohydr. Res., 303, 79-92. 

In describing and interpreting some of the more important properties of plant galactomannans, comparisons will be made with structurally similar polysaccharides, including the closely related glucomannans and galactoglucomannans, and those based on (1 — 4)-/3-D-xylan main-chains (for example, the arabinoxylans) and (1 — 4)-/3-D-glucan main-chains [for example, the amyloids and sodium 0-(carboxymethyl)cellulose]. 

Similar structural problems exist for the distribution of side chains in galactoglucomannans, xyloglucans, arabinoxylans, and 4-0-methylglucuronoxylans, and even for the distribution of acetyl groups in glucomannans and for related features in many other polysaccharides. 

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